You just edit your fstab!
All you need is here:
https://help.ubuntu.com/community/Fstab
The reason I wanted to do this is because the documents I synchronise with Sophia, the plan b directory of current project files, is on the windows partition of my laptop, as is good old Dropbox (in Ubuntu, the dropbox is a symlink to this directory on the windows partition – works a treat).
If I don’t mount the windows partition, I don’t automatically have access to it and can’t synchronise with Unison or run Dropbox.